First test of exotic space thruster ends in explosion

In 2006, Mason Peck at Cornell University in Ithaca dreamt up with an entirely new way to control satellites orbiting planets that have a magnetic field. The idea is based on the Lorentz force: that a charged particle moving through a magnetic field experiences a force perpendicular to both its velocity and the field.

So the plan is to somehow ensure that the spacecraft becomes electrically charged as it moves through the planetary magnetic field which should then generate a force that can alter the orbit or orientation of the vehicle. The big advantage of so-called Lorentz actuated orbit control is that it requires no propellant. That’s a big deal since the amount of fuel a spacecraft can carry is the main factor that determines its lifespan. Propellant-free propulsion could significantly increase their operaitng lives.

Today, Peck along with William Gorman and James Brownridge at the State University of New York at Binghamton present the results of the first experimental trials of the idea. The work was funded by NASA but it has to be said: it doesn’t look entirely promising.

The team tested the ability of various objects to hold a charge in a vacuum while being bombarded with plasma, as would be the case in orbit. To generate the charge on the test object, they attached it to a sample of radioactive Americium-24, an alpha-particle emitter, and applied a voltage. The electric field carries away the positively charged alpha particles leaving the object highly charged.

I’ll let the team take up the tale:

“Microscopic arcing was observed at voltages as low as -300 V. This arcing caused solder to explode off of the object.“

Obviously, a proplusion system that explodes while it is in operation needs some more work.

The early pioneers of experimental propulsion systems such as Robert Goddard and Werner von Braun all had to cope with catastrophic failures, so Peck, Gorman and Brownridge are in good company. And as long as nobody gets hurt, a decent explosion livens up any experiment.

So stick with it fellas. Something tells me that if NASA funds the future development of this system, we’re going to be in for some fun.

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on Friday, May 23rd, 2008 at 12:01 am and is filed under At the seaside, Mean machines.
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Relative to the ground? But this thing will be flying so much higher. I believe people are just making this stuff up. Space cannot really be charged, since it’s in a vacuum. Everyone knows this. Come on!

He meant relative to ground “neutral ground” or “common ground” not dirt ground. To give a very weird example if you were to take a set of jumper cables and place both black ends on a piece of metal(it does not have to be in the ground) that metal piece becomes “common ground”.

As others have written, voltage is relative to a reference (often called “ground.”) In transformers, for instance, the center-tap is usually the ground, and the two coil ends swing positive and negative in respect to that reference…

(Think of a sine wave, and the ground is the horiz line between the wave peaks and troughs…)

The charge of anything is the number of protons minus the number of electrons. A neutral object has equal numbers of both. It doesn’t matter if you’re talking about an atom or a satellite.

Im surprised they arent using electromagnets to generate a magnetic field that interacts with the planetary magnetic field… I guess very high charges is easier to maintain than high currents but still it seems difficult to control the charge.

Gawd. Can we please require at least a decent high school science education for anybody posting here?

Voltage is defined a the difference of electric potential in an electric field. If you have a potential difference of 300V between A and B, it’ll be -300V between B and A (for DX anyways.) If you swap the red and black jumper cables and attach them backwards, neither car/battery will like it (don’t try this at home, it’ll damage both cars/batteries and may melt the cable.)

This has *nothing* to do with where Ground or Earth is. That’s just a convention to simplify things so you don’t have to deal with differences all the time.

And… Space is not a vacuum. It is filled with atoms, ions and electrons. Just the pressure is waaay lower than on earth.

There is something I don’t get about this invention (although it’s a very interesting idea no matter what). If the point is to save propellant, how much is really saved if you do need to provide a power source to charge the satellite?

There is no such thing as DC current or AC current. That would be like calling it Direct current, current or Alternating current, current. I here it present that way so offten, even by engineers, that I just though I would bring it to your attention.

Not necessarily. Electronics get baked and age, but they’re generally in a Faraday cage (keeps out all but the hard stuff); the real lifetime limiter is stationkeeping fuel. Which is the point of looking into exotic prop (non-chem) solutions.

I am sure the reason they are not using electromagnets is related to the paradoxical principle stated in my favorite E&M text as “magnetic forces do no work”.

After all, if you take a close look at Maxwell’s Equations, you see that the force is always perpendicular to the direction of motion, therefore the dot product is zero: no work done.

In the satellite case, this means they could use magnetic forces to _spin_ the satellite, but not to raise and lower the height of its orbit. But if they use the force due to the _electric_ field, that _can_ do work.

What? That doesn’t make it clear? Well, I _did_ warn that it is paradoxical;)

This idea is poetic, with satellites floating on a magnetic field. It seems it would take a lot of power to do a useful amount of work, and there are difficulties in being charged significantly differently from your environment.